Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Patent
1985-12-02
1988-04-05
Louie, Won H.
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
430271, 430272, 430945, 430 21, 430495, 430961, G03C 178, G03C 172
Patent
active
047358890
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an optical recording medium and, more particularly, to a heat mode optical recording medium.
DESCRIPTION OF THE PRIOR ART
Optical recording media are designed to come into no contact with writing or reading heads and, therefore, are characterized by enjoying perfect freedom from deterioration by wear. This has incited various studies directed to development of optical recording media.
In the optical recording media, those of the heat mode are commanding particular interest of researchers because they have no use for any darkroom treatment for development.
The heat mode optical recording medium is an optical recording medium which utilizes the recording light in the form of heat. For example, the pit-forming type optical recording medium is based on the procedure of writing given information on the medium by forming small holes called pits by removing or melting off a part of the medium with a recording light such as a laser and reading the recorded information by sensing these pits with reading light. In the pit-forming type medium of this operating principle, particularly of the kind using a semiconductor laser permitting miniaturization of device, the recording layer is formed preponderantly of a material composed mainly of Te.
In recent years, increasing proposals and reports have come to cover those media which use recording layers of organic materials composed mainly of dyes in place of Te because Te type materials are harmful, and have to be sensitized to a higher degree and be produced at lower production costs.
Among the organic materials in the recording layers which require the He-Ne laser for the formation of pits, those using squalirium dyes [Japanese Patent Application Laid-open SHO 56(1981)-46,221 and V. B. Jipson and C. R. Jones.: J. Vac. Sci. Technol., 18, (1) 105 (1981)] and those using metal phthalocyanine dyes (Japanese Patent Application Laid-open No. SHO 57(1982)-82,094 and No. SHO 57(1982)-82,095) are included.
Another such organic material which similarly requires the He-Ne Laser uses a metal phthalocyanine dye (Japanese Patent Application Laid-open No. SHO 56(1981)-86,795).
These optical recording media invariably have their recording layers containing respective dyes deposited in the form of film by vacuum deposition and, in this sense, do not differ much from those using Te in terms of the production of recording medium.
Generally, since the laser beam impinging on the vacuum deposited film of dye has a low reflectance, the recording medium using this film fails to obtain an ample S/N ratio in the ordinary method of widespread acceptance which derives read signals from variations (decrease) in the amount of reflected light caused by pits.
When the optical recording medium is produced, which is of the so-called air-sandwich type construction having a recording layer opposed to and joined to a transparent substrate so that writing and reading of information is effected through the substrate, the recording layer can be protected from deterioration without lowering the writing sensitivity and the recording density can be improved. Even this recording and reproducing method is impracticable with the vacuum-deposited film of dye.
This is because, in the ordinary substrate made of transparent resin, the refractance has a certain value (1.5 in the case of polymethyl methacrylate) and the surface reflectance has a fairly large value (4% in the same resin) and the reflectance on the recording layer through the substrate is not more than about 60% in the case of polymethyl methacrylate, for example, and the recording layer which exhibits only a low reflectance, therefore, does not permit reliable detection of variations in the amount of reflected light.
For the purpose of improving the S/N ratio of reading of the recording layer formed of a vacuum deposited film of dye, a vacuum deposited reflecting film such as of Al is generally interposed between the substrate and the recording layer.
In this case, the purpose of the vacuum depos
REFERENCES:
patent: 4300143 (1981-11-01), Bell et al.
patent: 4383311 (1983-05-01), Ettenberg
patent: 4527173 (1985-07-01), Gupta et al.
Aoi Toshiki
Asami Shigeru
Kuroiwa Akihiko
Namba Kenryo
Takahashi Kazuo
Louie Won H.
TDK Corporation
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